This invention relates to diaphragm actuated relief valves and in particular to a bypass and pressure relief valve useful in internal combustion engine automotive systems. While the invention is described in detail with respect to automotive systems, those skilled in the art will recongnize the wider applicability of the invention disclosed hereinafter.
Diaphragm actuated bypass and relief valves, useful in automotive systems, are well known in the art. For example, the U.S. Pat. No. 3,520,320, to Crawford et al, issued July 14, 1970, discloses one particular form of a bypass and pressure relief valve. While the prior art in general, and the Crawford valve in particular, work well for their intended purpose, valves prior to the disclosure of the invention described hereinafter exhibited several disadvantages. For example, the bypass valve portion of the device described in the above-referenced Crawford et al patent operated against the bias of the main spring of the valve. While the pressure at which the relief valve operated could be varied, the amount of variation was limited by other overall considerations of valve operation. That is, in the bypass function of the diaphragm valve disclosed, the bypass valve portion operated against the spring pressure of the diaphragm spring which ordinarily is a relatively large spring requiring considerable force to overcome it. While some control is obtainable by varying the area of the valve member, such control was insufficient in all applications. In addition, prior art devices did not include means for controlling diaphragm movement. Consequently, large scale diaphragm movement was possible under the various modes of operation of an internal combustion engine in a motor vehicle, for example. Such large scale deflections of the diaphragm valve can reduce operating life of the diaphragm, the valve members or damage other exhaust systems components because the valve premits too high a quantity of air to enter the system.
The invention disclosed hereinafter eliminates these prior art deficiencies by providing a novel structural combination which includes integrally formed stop means for controlling diaphragm movement. Bypass relief is arranged so that a bypass valve operates against its own independent spring member, the spring constant of which may be preselected for a particular application. Consequently, greater operational flexibility is provided and valve life is improved. Limited diaphragm movement also limits the amount of air entering the exhaust system to an amount compatible with other system components.
One of the objects of this invention is to provide an improved valve structure having self-contained diaphragm stop means.
Another object of this invention is to provide a diaphragm operated bypass and pressure relief valve having an independent, positive acting valve for pressure relief.
Another object of this invention is to provide two positive acting valves on a single valve stem.
Other objects of this invention will become apparent to those skilled in the art in light of the following description and accompanying drawings.